Models Complex Terrain Dispersion

CTDMPFUS Complex terrain dispersion model plus algorithms for unstable situations SARA Superfund Amendments and Reauthorization Act... 

Perrv, S. G., Bums, D. J., Adams, L. A., Paine, R. J., Dennis, M. G., Mills, M. T., Strimaitis, D. G., Yamartino, R. J., and Insley, E. M., "User s Guide to the Complex Terrain Dispersion Model plus Algorithms for Unstable Conditions (CTDMPLUS)," Vol. I "Model Description and User Instructions," EPA/600/8-89/041, U.S. Environmental Protection Agency, Research Triangle Park, NC, 1989. 

Perry, S. G., Paumier, J. O., and Burns, D. J., Evaluation of the EPA Complex Terrain Dispersion Model (CTDMPLUS) with the Lovett Power Plant Data Base, pp 189-192 in "Preprints of Seventh Joint Conference on Application of Air Pollution Meteorology with AWMA," Jan. 14-18,1991, New Orleans, American Meteorological Society, Boston, 1991. Bums, D. ]., Perry, S. G., and Cimorelli, A. ]., An advanced screening model for complex terrain applications, pp. 97-100 in "Preprints of Seventh Joint Conference on Application of Air Pollution Meteorology with AWMA," Jan. 14-18, 1991, New Orleans, American Meteorological Society, Boston, 1991. 

CTDMPLUS Complex terrain dispersion model plus algorithms for... 

Gaussian puff/plume dispersion modeling techniques embedded in D2PC are representative of the state of the art in the late 1970s. Since then, there have been many technical advances in understanding atmospheric turbulence, boundary layer structure, and the effects of complex terrain that could benefit the CSEPP program. 

The D2-Puff model, and other plume dispersion models, can be calibrated for the effects of complex terrain at specific sites by experimental releases and downwind measurements of an inert gaseous bacer under a variety of representative meteorological conditions. These calibrations can significantly enhance the accuracy of dispersion calculations from specific fixed sites like chemical agent storage yards and demilitarization facilities. 

Because of very complex terrain the application of simple dispersion models is very limited in Slovenia. Traffic pollution and the high level of surface ozone are the main current air pollution problems in the country. No official standard model for regulatory purposes has been accepted in Slovenia up to present. The US EPA model ISC3 is used for routine dispersion calculations from point sources. Some other imported models were tested in Slovenia but only on research basis. A neural network forecasting model was developed for the Sostanj thermal power plant. No urban air pollution studies are reported from Slovenia. Air pollution modelling is performed at the Jozef Stefan Institute, Dept, of Environmental Sciences, Ljubljana, Slovenia (US, 2005), AMES d.o.o. and the Hydrometeorological service. 

The CFD simulation is conducted solely considering obstacles such as some equipments, buildings and devices present on the surroundings of the source point. No complex terrain is taken under consideration for the gas flow. Most of puff models consider stability classes as there are changes for the dispersion coefficients. Here, different turbulence models, with different eddy diffusivities are used to represent conditions of low turbulence level, consequently a more persistent condition, at night, and the opposite during a day release. 

For simple situations where plume direction is dominated by wind direction only, using arc-wise maximum concentrations together with plume width is the recommended procedure. However, for other situations, such as dispersion close to buildings or in complex terrain, part of the model performance depends on the correct prediction of the plume path, or there may not even be a unique plume path. In those situations, comparisons of concentration or dose paired in space should be included. In those cases, the experimental data points (sensor positions) included in the comparison should be restricted to points that give significant information about the location and behavior of the plume or cloud, i.e., the number of zero-level measurements should be restricted, though zero-level measurements contain valuable information. 

Of all the approaches, the k-6 model offers the highest relative independence of empirical relations. It appears to be the only one to allow a proper simulation of hydrogen dispersion, because it meets the requirements of describing effects such as turbulence energy in the gas cloud, interaction of the cloud with the atmospheric wind field, the characteristic positive buoyancy, transient sources with initial momentum, and last but not least, gas flow in a complex geometry (buildings, terrain). K-e modeling has been realized in a variety of... 

Most releases are influenced by buildings or structures either at the source or during the dispersion of the plume. Most available models are unable to handle these complexities well they are suitable only for dispersion over flat, homogeneous terrain. 

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